title: Na7Al3(As2O7)4.
abstract: The title compound, hepta-sodium trialuminium tetrakis(diarsenate), has been isolated as single crystals from a solid-state reaction. Its structure, which is isotypic with that of the Na7Fe3(X 2O7)4 (X = As, P) family of compounds, consists of AlO6 octa-hedra sharing their vertices with As2O7 groups, forming a three-dimensional [Al3(As2O7)4]∞ framework incorporating channels occupied by the sodium ions. One of the aluminium ions lies on a crystallographic twofold axis. The sodium ions are situated over ten positions (one with site symmetry 2), all but one of which are partially occupied.
authors.affiliation: Laboratoire de Matériaux et Cristallochimie, Faculté des Sciences de Tunis, Université de Tunis El Manar, 2092 Manar II Tunis, Tunisia.
authors.forename: Noura
authors.initials: N
authors.lastname: Fakhar Bourguiba
authors.forename: Ahmed
authors.initials: A
authors.lastname: Driss